The Cotswold water park consists of over 133 lakes created by gravel extraction, covering over 40 square miles - 50% larger than the Norfolk Broads and still growing. Outstanding countryside provides the setting for relaxation and discovery for adults and children alike - perfect for a family day out, walkers, birdwatchers, photographers and outdoor enthusiasts. Further information about the water park is here.
The Thames path runs from it's source just up the road from this location, near Cirencester. At this point the Thames is already a proper river although it has yet to grow to it's full size. Further details are here.
There is parking for two cars at N51°38.761', W01°56.529'.
Please check out the Geocaching Association of Great Britain offering support for Geocachers in GB.